An intrauterine device is a device placed in the uterus, also known as an IUD. The IUD is the world's most widely used method of reversible birth control [1], currently used by nearly 160 million women, just over two-thirds of whom are in China, where it is the most widely used birth control method [2]. Usage in many countries has been measured by surveys of married women of reproductive age. In this population in the early 1990s, IUD use ranged from 1.5% in North America, to 18% in Scandinavia, 33% in Russia and China, and 40% in Kazakhstan [20]. The use in China has increased to 45% of married women by 2002[2].
The insertion and removal of the IUD into and from the uterus has to be performed by a doctor or qualified medical practitioner. Generally, it remains in place for the entire period of undesired pregnancy. However, practically, depending on the type, a single IUD is approved for 5 to 10 years.
The presence of a device in the uterus prompts the release of leukocytes and prostaglandins by the endometrium. These substances are hostile to both sperm and eggs. It is reported that the presence of copper increases this spermicidal effect [18][19].
Early designed IUDs are coil-shaped based. The first plastic IUD, the Margulies Coil or Margulies Spiral, was introduced in 1958. This device was somewhat large, causing discomfort to a large proportion of women users, and had a hard plastic tail, causing discomfort to their male partners.
The stainless steel single-ring IUD was developed in the 1970s [5] and widely used in China because of low manufacturing costs. The Chinese government banned production of steel IUDs in 1993 due to high failure rates (up to 10% per year) [6] [7].
The plastic T-shaped IUD was conceived in 1968. Shortly thereafter, the idea of adding copper to the devices, in order to improve their contraceptive effectiveness was introduced [3] [8]. It was found that copper-containing devices could be made in smaller sizes without compromising effectiveness, resulting in fewer side effects such as pain and bleeding [9]. T-shaped devices had lower rates of expulsion due to their greater similarity to the shape of the uterus [4].
Second-generation copper-T IUDs were also introduced in the 1970s. These devices had higher surface areas of copper, and for the first time consistently achieved effectiveness rates of greater than 99%. Nevertheless these T-shaped designed IUDs have several drawbacks, causing significant undesirable symptoms to the women.
As is known there are two broad categories of intrauterine contraceptive devices: inert and copper-based devices, and hormonally-based devices that release progestogen.
Non-hormonal IUDs
Most of the non-hormonal IUDs have a plastic T-shaped frame that is wound around with pure electrolytic copper wire and/or has copper collars (sleeves). All copper-containing IUDs have a number as part of their name. This is the surface area of copper (in square millimeters) the IUD provides.
In some IUDs, the pure copper wire has a silver core which has been shown to prevent breaking of the wire [10 [12].
The arms of the frame hold the IUD in place near the top of the uterus. The GyneFix does not have a T-shape, but rather is a loop that holds several copper tubes. The GyneFix is held in place by a suture to the fundus of the uterus.
In the following conditions, the insertion of a copper IUD is not usually recommended:                Postpartum between 48 hours and 4 weeks (increased IUD expulsion rate with delayed postpartum insertion)        Benign gestational trophoblastic disease        Ovarian cancer        Very high individual likelihood of exposure to gonorrhea or chlamydial STIs        AIDS (unless clinically well on anti-retroviral therapy)        Cervical cancer (awaiting treatment)        Endometrial cancer        Distortions of the uterine cavity by uterine fibroids or anatomical abnormalities        Current PID        Known pelvic tuberculosis        
Another disadvantage of the copper IUD concerns women with metal sensitivities to copper or nickel whom may experience adverse reactions from an IUD. The metal used in IUDs is 99.99% copper, with one study finding a maximum nickel content of 0.001%. Because nickel has a relatively high sensitizing potential, a few researchers suggested even this tiny amount might be problematic.
Moreover, after IUD insertion, menstrual periods are often heavier, more painful, or both, especially for the first few months after they are inserted. On average, menstrual blood loss increases by 20-50% after insertion of a copper-T IUD. Increased menstrual discomfort is the most common medical reason reported for IUD removal [16].
Hormonal Intra-Uterine Devices
One of the main advantageous of hormonal uterine devices is that they do not increase bleeding as inert and copper-containing IUDs do. Rather, they reduce menstrual bleeding or prevent menstruation altogether, and can be used as a treatment for menorrhagia (heavy periods).
Although use of hormonal intra-uterine devices results in much lower systemic progestogen levels than other very-low-dose progestogen-only hormonal contraceptives, they might possibly have some of the same side effects.
Progestasert was the first hormonal uterine device, developed in 1976[13] and manufactured until 2001[14]. It released progesterone, was replaced annually, and had a failure rate of 2% per year [15].
As of 1997, the LNG-20 IUS—marketed as Mirena by Bayer is the only IntraUterine device available. First introduced in 1990, it releases levonorgestrel (a progestogen) and may be used for five years.
The main side effects and complications of the hormonal IUDs include:                Uterine perforation, especially when the uterine walls are soft or more fragile (after pregnancies, endometritis, adenomyosis etc.). The perforation rate is relatively rare (about 0.5% to about 1%); however, it is probably underestimated due to under reporting.        Expulsion—more common in younger women, women who have not had children, and when an IUD is inserted immediately after childbirth or abortion.        The risk of ectopic pregnancy in pregnancies that do occur during IUD use is higher than the expected percentage (3-4%) [17].        Mal-position of the IUD may increase the rate of undesirable pregnancies. If pregnancy does occur, the presence of the IUD increases the risk of miscarriage, particularly during the second trimester. Even when the IUD is removed in the beginning of the pregnancy, there is still a risk for premature delivery.        The rate of misplacement (the combination of perforation, expulsion and mal-position in the uterus) is at least 3%.        
Therefore, it is desirable to have intrauterine devices which overcome the abovementioned drawbacks. There is still a long felt need for IUDs which can be safely and conveniently inserted into the uterine cavity, without causing perforation of the uterine walls. Furthermore, there is still a long felt need to provide IUDs with reduced expulsion and mal-position rates. Such an IUD will reduce the need for unnecessary surgeries and is expected to have less undesirable side effects.